Aragonite Crystal Growth and Solid-State Aragonite–Calcite Transformation: A Physico–Geometrical Relationship via Thermal Dehydration of Included Water

Koga, Nobuyoshi; Kasahara, Daisuke; Kimura, Tomoyasu

doi:10.1021/cg400350w

Cited by 53 publications

(49 citation statements)

References 66 publications

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“…Other methods, such as solution mixture 8,79 and hydrothermal synthesis, 88 can also produce spherulitic aragonite with different additives and thermal treatments. Aragonite spherulites synthesized from different methods, however, can have different morphologies.…”

Section: Methodsmentioning

confidence: 99%

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

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Coral skeletons were long assumed to have a spherulitic structure, that is, a radial distribution of acicular aragonite (CaCO 3 ) crystals with their c-axes radiating from series of points, termed centers of calcification (CoCs). This assumption was based on morphology alone, not on crystallography. Here we measure the orientation of crystals and nanocrystals and confirm that corals grow their skeletons in bundles of aragonite crystals, with their caxes and long axes oriented radially and at an angle from the CoCs, thus precisely as expected for feather-like or "plumose" spherulites. Furthermore, we find that in both synthetic and coral aragonite spherulites at the nanoscale adjacent crystals have similar but not identical orientations, thus demonstrating by direct observation that even at nanoscale the mechanism of spherulite formation is non-crystallographic branching (NCB), as predicted by theory. Finally, synthetic aragonite spherulites and coral skeletons have similar angle spreads, and angular distances of adjacent crystals, further confirming that coral skeletons are spherulites. This is important because aragonite grows anisotropically, 10 times faster along the c-axis than along the a-axis direction, and spherulites fill space with crystals growing almost exclusively along the c-axis, thus they can fill space faster than any other aragonite growth geometry, and create isotropic materials from anisotropic crystals. Greater space filling rate and isotropic mechanical behavior are key to the skeleton's supporting function and therefore to its evolutionary success. In this sense, spherulitic growth is Nature's 3D printing. KEYWORDS: Ion attachment, crystallization by particle attachment, CPA, biomineralization, PEEM, PIC-mapping, mesocrystal S pherulites are polycrystalline structures in which acicular crystals radiate from a common center and grow approximately synchronously so the final shape of a spherulite resembles a sphere. 1−7 Figure 1 shows two types of spherulites: "spherical spherulite", in which the crystal fibers start from a point, or "plumose spherulite", in which crystal fibers radiate at an angle from the line. 7 Spherulites start forming as an aggregate of parallel acicular crystals termed "fibers", then form a "sheaf of wheat" structure, and with the growth of more fibers eventually become complete spheres. 8 In an ideal spherulite, fibers radiate from the center and contain all possible orientations within the sphere. Since the fast-growing axis in aragonite (CaCO 3 ) is the c-axis, 9 in spherulites each fiber elongation direction coincides with the crystalline c-axis. 10,11 In real spherulites, biogenic 12 and synthetic, 7 the crystal orientations are not perfectly radial nor continuously varying with angle, they deviate slightly from radial and exhibit small but abrupt changes in orientation, termed "branching". In Figure 1 branching angles are smaller than 30°in direction and in crystal lattice orientation. This is distinct from crystallographic branching, which occurs in sno...

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Section: Methodsmentioning

confidence: 99%

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

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“…Each of these polymorphisms possesses different properties which determine their special characteristics [5]. In fact, numerous studies on both the physical and chemical properties of calcium carbonate polymorphisms have been accomplished since several decades ago [2,3,5,[12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Cockle Shell-Based Calcium Carbonate Aragonite Polymorph Nanoparticles with Surface Functionalization

Ghafar

Hussein

Zakaria

2017

Journal of Nanoparticles

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The development of cockle shell-based calcium carbonate aragonite polymorph nanoparticle synthesis method using the technique of mechanical stirring in the presence of dodecyl dimethyl betaine (BS-12) incorporated with surface functionalization demonstrated high homogeneity of sample product with good nanoparticles dispersion. The cockle shell-based calcium carbonate aragonite nanoparticle with functionalized surface was characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), particle size distribution, pH measurement analysis, Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). Surface functionalization was proven to improve the overall size and shape of the nanoparticles and enhance their dispersion properties, preventing coarse agglomeration among nanoparticles in general. The improved method was verified to retain its aragonite crystalline nature. Additionally, surface functionalization did not increase the size of nanoparticles throughout the modification process. This facile preparation using naturally occurring cockle shells as the main source is environmentally friendly because it provides relatively low cost of raw material source as it is abundantly available in nature and has good mineral purity content. Hence, high quality production of surface functionalized cockle shell-based calcium carbonate aragonite polymorph nanoparticles can potentially be exploited and produced on a large scale for various industrial applications, especially for biomedical purposes in the near future.

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“…CaCO3 exists in calcite of cubic form, aragonite of spherical form, and vaterite of columnar form, of which cubic calcite is most stable [33]. Aragonite transforms into calcite at 380-470 °C, and vaterite is the most unstable [34,35].…”

Section: Discussionmentioning

confidence: 99%

CO2 Fixation by Membrane Separated NaCl Electrolysis

et al. 2015

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Atmospheric concentrations of carbon dioxide (CO2), a major cause of global warming, have been rising due to industrial development. Carbon capture and storage (CCS), which is regarded as the most effective way to reduce such atmospheric CO2 concentrations, has several environmental and technical disadvantages. Carbon capture and utilization (CCU), which has been introduced to cover such disadvantages, makes it possible to capture CO2, recycling byproducts as resources. However, CCU also requires large amounts of energy in order to induce reactions. Among existing CCU technologies, the process for converting CO2 into CaCO3 requires high temperature and high pressure as reaction conditions. This study proposes a method to fixate CaCO3 stably by using relatively less energy than existing methods. After forming NaOH absorbent solution through electrolysis of NaCl in seawater, CaCO3 was precipitated at room temperature and pressure. Following the experiment, the resulting product CaCO3 was analyzed with Fourier transform infrared spectroscopy (FT-IR); field emission scanning electron microscopy (FE-SEM) image and X-ray diffraction (XRD) patterns were also analyzed. The results showed that the CaCO3 crystal product was high-purity calcite. The study shows a successful method for fixating CO2 by reducing carbon dioxide released into the atmosphere while forming high-purity CaCO3. OPEN ACCESSEnergies 2015, 8 8705

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Aragonite Crystal Growth and Solid-State Aragonite–Calcite Transformation: A Physico–Geometrical Relationship via Thermal Dehydration of Included Water

Cited by 53 publications

References 66 publications

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Synthesis and Characterization of Cockle Shell-Based Calcium Carbonate Aragonite Polymorph Nanoparticles with Surface Functionalization

CO2 Fixation by Membrane Separated NaCl Electrolysis

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